MISSISSIPPI STATE -- Cattle and pregnant horses could suffer serious health problems this spring from a grass intended for cool-season nourishment.

Dr. Michael Brashier, an assistant professor at Mississippi State University's College of Veterinary Medicine, encouraged veterinarians to be on the lookout for fescue toxicity. Brashier addressed the concern during the recent meeting of the Mississippi Veterinary Medical Association.

"Pregnant mares are especially at risk of fescue toxicity every spring when the grass is growing the fastest," Brashier said. "Effected mares may abort their foals, have little or no milk, or have extended pregnancies and produce oversized foals. Still births are not uncommon as well as other complications for the mother from an oversized baby."

Fescue is the most important cool-season grass in the United States with about 35 million acres planted nationally and 600,000 acres in Mississippi. Fescue toxicity results from an invisible fungus in the grass, primarily when the grass is growing rapidly.

Unlike horses, cattle may experience problems related to blood circulation.

"Commonly called fescue foot, cows may become lame or actually lose their feet or tails because of poor circulation. Cows' overall health can be weakened by fescue," Brashier said.

The damaging effects of fescue can be lessened by diluting it with other forages or feeds. Pasture rotation is another effective management technique.

"The quantity of fescue is the main factor, but whenever possible, owners should remove pregnant mares completely from fescue pastures or hay by their last trimester to avoid complications," Brashier said. "If eliminating fescue isn't an option, veterinarians have domperidone oral supplements they can give to protect the animals."

When a foal is produced while the mother is on fescue, owners may need veterinarians to give the baby plasma if the first milk is not available and to give the mare a prescribed medicine to help her milk develop.

"Foals are pretty fragile and will die quickly without the proper nutrients," Brashier said. "They are very dependent on the colostrum, or first milk, for protection against infection."

Fungus-free fescue varieties are available for livestock. The original fescue with the fungus continues to be available because it appeals to turf managers and others for its resistance to certain pests.

Brashier said livestock owners may not know if their animals are feeding on fungus-infected fescue.

Extension county agents can assist owners in determining if their animal's feed is fungus-infected fescue.